The problem with pool noodle port blockers are that they inherently beg to be pulled out. Once you pull them out you have to put them back in, and once it's okay to put stuff in the port holes you've created a bigger problem than you've solved.
I think speaker grills are perfect
Marked a line on the cement and another line on the front tire with a piece of chalk, got on the bike, lined up the two lines and rolled forward one revolution and made another chalk mark on the cement.
Measured the distance between the chalk marks and then plugged that into the cateye.
(the size chart in the cateye manual was off by 12mm)
Google maps said today's route was 32.4 miles, the cateye said 32.3 miles.
Close enough.
Somewhat seriously. Some subs have foam inserts you can use to block the ports off. Look like a cut up pool noodle....
Also, I would be way more nervous about the drivers (even with grills) ... this coming from someone with kids and some dented drivers. In this case I would recommend upgrading to electrostatics, as they offer greater... "deterrent"